Safety joint



Feb. 13, 1968 B. Q. BARRINGTON ETAL SAFETY JOINT Filed Aug. lO, 1965 2Sheets-Sheer l FIG. 2

INVENTOR BURCHUS Q. BARRINGTON SEVERO L. VILLALON, JR.

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ATTORNEYS.

Feb. 13, 1968 B. Q BARRINGTON ETAL 3,368,829

SAFETY JOINT 2 Sheets-Sheel 2 Filed Aug. 10, 1965 dii INVENTOR BURCHUSQ. BARRINGTON SEVERO L. VILLALON, JR.

ATTORNEYS,

United States Patent Otice 3,368,829 Patented Feb. 13, 1968 ABSTRACT FTHE DISCLGSURE A safety joint for releasably coupling well tubingtogether in a string. The joint includes a threaded cap, a mandrel, anda case. The mandrel extends through the cap which is screwed into thecase. Rotary motion of the mandrel is transmitted to the cap by a splinea-nd slot arrangement. Splines in the case cooperate with lugs on themandrel to restrict rotation of the cap by the mandrel except during aseries of alternating rotating and reciprocating movementsof themandrel. A springcollar and a ring are mounted in coaxial relationbetween the case and the mandrel, so that during axial movement of themandrel, the ring engages projections on the spring collar to resistaxial movement of the mandrel. When a predetermined axial force isapplied to the mandrel, the ring deects the projections on the springcollar radially to allow the ring to pass through the collar, therebygiving a positive indication at the surface of the relative position ofthe mandrel and the case.

This invention relates to pipe joints, and more particularly to safetyjoints for pipe strings that are used in oil and gas wells.

It is common practice to provide a safety joint in a drill pipe stringthat is run in a bore hole or well. The safety joint is usually made upin the string above a tool that may become lodged in the bore hole, suchas a packer assembly. If a tool should be stuck in the hole and cannotbe jarred loose, it becomes necessary to break the safety joint so thatonly a minimum number of tools are left inthe hole.

A safety joint is often provided immediately above a packer assembly inthe string. Inl order to expand the packer, it is usually necessary tomanipulate the string by vertical or rotational movement to cause thepacker elements to expand. The coupling in a conventional safety jointis manipulated in the same manner to cause separation or releasing ofthe safety joint. Accordingly, the use of certain conventional safetyjoints with packer assemblies having similar manipulation procedures maycause the safety joint to be released prematurely, or the threads in thesafety joint may begin to back oftp without the operator being aware ofit.

Another problem is that it may be necessary to carry out operations inholes in which the iiuid contains sand or foreign material. The sand orforeign material may enter the safety joint and prevent the safety jointfrom releasing properly.

In view of the defects of previous safety joints, it is an object ofthis invention to provide an improved safety joint.

It is a further object of this invention to provide a safety joint thatdoes not become released accidentally when other tools in the string aremanipulated.

It is a still further object of this invention to provide a safety jointwhich operates effectively in conditions where sand or foreign materialare present in the well Huid.

These objects are accomplished in accordance with a preferred embodimentof the invention by a safety joint including a mandrel that is mountedin telescoping relation in a case. The mandrel has a radial spline whichengages an internal slot in a tubular cap which is threaded on the caseand extends along the external surface of the mandrel. A portion of thecap 3 engages the upper end of the spline on the mandrel and preventsthe mandrel from being displaced out of the case. The case has aplurality of internal, circumferentially spaced axial splines whichcooperates with a pair of lugs on the mandrel. The internal splines onthe case do not extend the full length of the case but are offsetaxially from adjacent splines to allow the lugs to pass across the endof each spline. Thus, the mandrel may be rotated relative to the case bya series of axial and rotational steps.

Cooperation of the spline on the mandrel with the internal slot in thecap causes the cap to be unscrewed as the mandrel is rotated relative tothe case. A latch spring is mounted between the case and the mandrel toprovide a positive indication at the surface that the mandrel isrotating relative to the case. A ring on the mandrel engages the latchspring, which imposes a resistance to vertical movement of the mandrel.The resistance of the latch spring is of sucient magnitude to berecorded at the surface on each upward and downward movement of themandrel as the ring passes through the latch. The cap seals the interiorof the case from the well fluid, so that sand or foreign materials whichmight be present in the well fluid cannot enter the space between themandrel and the case. The case has bypass ports which are covered by themandrel. The ports remain covered during the manipulation of the mandrelrelative to the case. Just prior to the point where the cap is fullyunscrewed, the ports are uncovered by axial movement of the mandrel toequalize the pressure on the inside and outside of the case. The cap isthen released by further rotation of the mandrel.

This preferred embodiment is illustrated in the accompanying drawings inwhich:

FIG. 1 is a cross sectional view of the safety joint of this invention;

FIG. 2 is a cross sectional view of the latch spring;

FIG. 3 is an enlarged cross sectional view of the safety joint along theline 3 3 in FIG. 1;

FIG. 4 is an enlarged cross sectional view of the safety joint along theline 4-4 in FIG. l;

FIG. 5 is a detail cross sectional view of the upper portion of thecase; and

FIG. 6 is a cross sectional view of the safety joint after the cap hasbeen partially unscrewed.

Referring to FIG. l, the safety joint of this invention includes atubular mandrel 2, which is mounted in telescoping relation in a case 4.The mandrel 2 has a single radial spline 6 and a pair of lugs 8projecting on opposite sides of the mandrel 2. As shown in FIG. 3, thespline 6 is aligned with one of the lugs 8 on the mandrel.

A cap 10, having an externally threaded portion 12 at one end, engagesinternal threads 14 in t-he case 4. At the opposite end of the cap 10,an annular ring 16 prevents the entry of fluid into the interior of thecap along the mandrel 2. The cap 10 also has an internal slot 18 whichreceives the spline 6 on the mandrel. The wide clearance between thesides of the slot 18 and the spline 6, as shown in FIG. 3; prevents theslot from caking up with mud, if any should reach the interior of thecap 10. The slot 18 allows the mandrel to move longitudinally relativeto the cap 10, but restricts rotational movement of the cap relative tothe mandrel. The threads 12 and 14 are oriented in such a way that theslot 18 is aligned with the space between adjacent splines 2l) and 22 toallow the mandrel 2 to move longitudinally relative to the cap and case.

The case 4, as shown in FIG. 5, has two pairs of axial splines 20 and22. The upper splines 2t) project from diametrieally opposite sides ofthe case 4, as shown in FIG. 4. The lower splines 22 are spaced at 90from the upper splines 20 and project from opposite sides of the case 4.The upper splines 20 terminate slightly below the upper ends of thelower splines 22 and the adjacent ends of the splines 20 and 22 areformed by plugs 24 which are welded or otherwise secured in the case 4.The splines 20 and 22, as shown in FIGS. l and 5, require the mandrel tobe displaced axially a sufficient distance for the lugs 8 to clear theends of the respective splines 20 and 22 in order to rotate the mandrelmore than a half turn relative to the case 4. Thus, in order to rotatethe mandrel, it is necessary to displace the mandrel downwardly as thelugs 8 slide along the side of the splines 20 until the lugs 8 are belowthe plug 24 at the end of the splines 20. Then the mandrel is rotated aquarter turn until the lugs 8 engage the splines 22. The mandrel is thenraised until the lugs 8 are displaced above the plugs 24 at the upperends of the splines 22. The process is then repeated to continuerotation of the mandrel relative to the case 4.

Below the splines 22 is a spring collar 26 that is mounted in the case4, between the case and the mandrel 2. The upper end of the collar 26engages the lower end of the splines 22 and upward movement of thecollar is restrained by the splines 22. A sleeve 28 is threadedlysecured to the lower end of the case 4 and the upper end of the sleeve28 projects into the interior of the case 4 to form a seat whichsupports the lower end of the spring collar 26. Thus, the collar 26 isfixed against movement relative to the case 4 by the splines 22 and thesleeve 28. The spring 26, as shown in FIG. 2, has a plurality of axialslots 30 spaced uniformly around the circumference of the collar to formstrips 32. The center of each strip 32 is capable of resiliently flexingin a radial direction. Projections on each of the strips 32 form cams 34approximately midway of the length of the strips. The cams 34 are on theinterior of the collar for displacing the central portions of the stripsoutwardly from the center of the collar 26.

A tube 36 is threadedly secured to the lower end of the mandrel 2 and alatch ring 38 is clamped between a shoulder on the mandrel 2 and theupper end of the tube 36. The latch ring 38 has a diameter slightlylarger than the internal diameter of the cams 34 on the collar 26, sothat upon axial displacement of the mandrel 2, the ring 38 engages thecams 34 to urge the strips 32 outwardly as the ring passes over thecams. Adjacent the lower end of the tube 36, a seat 40 is formed in thesleeve 28 and a shoulder 42 on the tube 36 engages the seat 40 to limitthe downward displacement of the mandrel 2 relative to the case 4.Bypass ports 44 are provided in the sleeve 28 and sealing rings 46prevent fluid communication between the bypass ports 44 and the interiorof the mandrel 2 until the tube 36 is raised sufficiently for theshoulder 42 to be positioned above the sealing rings 46, which occursjust before the cap is unscrewed from the case 4.

The relative positions of the mandrel and the case during rotation ofthe cap 10 are shown in FIG. 6. When the mandrel is raised sufficientlyfor the lugs 8 to pass over the upper ends of the lower spline 22, themandrel is in the position shown in FIG. 6 and the latch ring 38 on themandrel 2 is displaced above the cams 34 on the collar 26. In order tocause the ring 38 to pass through the collar, it is necessary to applyan upward force on the mandrel of a sufficient magnitude to displace thecenter of the strips 32 outwardly. The upward force required to operatethe latch ring and collar combination should be in the range of between8,000 and 12,000 pounds. On the downward stroke, the lower cam surfaceon the exterior of the latch ring 38 has a lower slope than the uppercam surface on the ring, and accordingly, less force is required to beapplied to displace the ring through the collar. Tubing weight in therange of between 3,000 and 6,000 pounds may be required to displace thelatch ring 38 through the collar 26 on the downward stroke. As analternative, the

ring 38 may be positioned closer to the lugs 8 than is shown in FIG. l,so that it is necessary for the ring to pass through the collar 26 onlyon the initial stroke.

In operation, the safety joint of this invention is made up in a tubingstring. The threads on the upper end of the mandrel 2 are secured in thetubing string by a conventional tubing collar, and the threads on thelower end of the sleeve 28 are secured to a packer or other tool, or apipe section by a conventional tubing collar. The safety joint isassembled as shown in FIG. l, with the external threads 12 on the cap 10engaging the full length of the threads 14, so that the slot 18 wiIl bealigned with the space between the splines in the case. When the mandrelis in the position shown in FIG. 1, rotational movement is transmittedfrom the mandrel to the case by means of the lugs 8 which engage thelower splines 22 in the case.

Downward axial force on the mandrel is transmitted to the next lowerpipe section or tool by the shoulder 40 on the sleeve 28. Upwardmovement of the mandrel relative to the case is limited by engagement ofthe latch ring 38 with the cams 34 on the collar 26. However, if thespring force of the collar is exceeded, the lugs 8 engage the lower endof the cap 10 and thereby limit longitudinal displacement of the mandrelrelative to the case. By this arrangement, the weight of the tubing canbe set down on a packer that is below the safety joint to cause thepacker to expand.

When itis desired to uncouple the safety joint an upward force isapplied to the tubing string to draw the latch ring 38 through thecollar 26. Right hand torque is applied to the tubing string to rotatethe mandrel until the lugs 8 engage the side of the splines 20. The case4 resists longitudinal and rotational displacement in the hole since itis coupled to an expanded packer or other tool. The tubing weight isthen applied to lower the mandrel 2 until the latch ring passes backthrough the collar 26. When the latch ring is below the cams 34, theupper end of the lugs 8 are suiciently below the lower end of the uppersplines 20 to allow rotation of the mandrel 2 until the lugs 8 engagethe side of the lower splines 22. Upward and downward movement of themandrel is continued, while applying a right hand torque to the mandrel,until the cap 10 is unscrewed. The spline 6 on the mandrel moves throughthe slot 18 as the mandrel is raised and lowered relative to the case 4.The spline 6 applies a rotational torque to the cap 10. When the cap 10is almost fully unscrewed from the case 4, the tube 36 on the lower endof the mandrel is raised sutliciently for the shoulder 40 to bedisplaced above the relief ports 44 to allow Huid communication betweenthe interior of the mandrel and the exterior of the sleeve 28. As shownin FIG. 5, the internal diameter of the case 4 is substantially uniformabove the splines 22 to allow the lugs 8 to pass out of the upper end ofthe case 4 when the cap 10 has been separated from the case. The spline6 on the mandrel engages the upper end of the cap 10 at the upper end ofthe slot 18 to raise the cap along with the mandrel. The case 4, thecollar 26 and the sleeve 28 remain in the hole.

Since the interior of the case 4 is not exposed to fluids in the borehole, the safety joint operates Vsuccessfully in well fluids thatcontain sand or foreign material. Furthermore, the safety joint of thisinvention permits manipulation of the pipe string by upward and downwardmovement and rotational movement for operating a tool, such as a packer,below the safety joint, without accidentally releasing the safety joint.The latch ring 38 provides a positive indication at the surface ofraising and lowering of the mandrel relative to the case 4, so that theoperator is warned when the latch ring passes through the collar 26 tobegin unscrewing the safety joint.

While this invention has been illustrated and described in oneembodiment, it is recognized that variations and changes may be madetherein without departing from the invention set forth in the claims.

We claim:

1. Coupling apparatus for releasably securing together tubing comprisinga case, a mandrel mounted in said case in telescoping relation, a ca'p,said cap having one end threadably secured to said case, one of said capand said mandrel having a slot therein and the other having a splineextending into said slot, cooperating means on the exterior wall of saidmandrel and the interior wall of said case for resisting rotation ofsaid mandrel relative to said case, said cooperating means including alug on one of said mandrel and case and apair of splines on the other ofsaid mandrel and case, said splines being rotationally spaced from eachother about the central axis of said mandrel and said case, and saidsplines being axially offset from each other to allow rotation of saidmandrel relative to said case only upon axial reciprocation of saidmandrel relative to said case, limit means including shoulders on saidmandrel and said case, said shoulders being in position for preventingaxial displacement of said mandrel relative to said case beyond a firstaxial position and a second axial position, a tubular collar disposedbetween said mandrel and said case, said collar having a plurality ofaxial slots therein and having a plurality of internal projectionsbetween adjacent slots, said projections being aligned in -a radialplane of said collar, a ring carried by said mandrel, said ring havingcam surfaces on opposite ends thereon, means mounting said collar andsaid ring for relative axial movement upon axial displacement of saidmandrel relative to said case, said ring engaging said collar projectionupon axial displacement of said mandrel to an axial positionintermediate said first and second positions, whereby the ring engagesthe projections on the collar and yieldably resists movement of themandrel relative to the case.

2. Coupling apparatus according to claim 1 wherein said cap is ofsuicient length to enclose said slot and spline during said axialdisplacement of the mandrel relative to the case, whereby the slot andspline are not ex posed to fluid that may be present on the exterior ofthe lcoupling apparatus.

3. Coupling apparatus according to claim 1 wherein said cooperatingmeans includes a lug and axial splines cooperating to prevent relativerotation between said mandrel and said case beyond a predeterminedrotational angle in both of said first and second axial positions.

4. Coupling apparatus according to claim 2 wherein said cap isthreadably secured at one end to said case, the opposite end of said caphaving a central opening therein, said mandrel extending through saidcap opening, and seal means secured between said mandrel and said cap atsaid opening.

5. Coupling apparatus according to claim 1 wherein said splines areoffset axially from adjacent splines to define transverse openings toallow said lug to .pass over the end of one of said splines uponrotation of said mandrel while at one of said first and second axialpositions, said collar and said ring being displaced into engagementwith each other upon said axial displacement of said lug from said firstto said second axial positions.

6. Coupling apparatus according ot claim 1 wherein said splines areoffset axially from adjacent splines to define transverse openings toallow said lug to pass over the end of one of said splines upon rotationof Said mandrel while at one of said rst position and a third position,said third position being intermediate said irst and second positions,said ring engaging said collar projections upon said axial displacementbetween said second axial position and said third axial position.

7. Coupling apparatus yaccording to claim 1 wherein said ring is securedcoaxially on said mandrel, means securing said collar coaxially in saidcase, said ring and said collar projections having an interference ittherebetween, whereby the projections yieldably resist axial movementrelative to the collar.

8. Coupling apparatus according to claim 1 wherein one of said ring camsurfaces have a greater slope than the other, whereby a greater axialforce is required to displace the ring axially over the projections inone direction than in the other.

References Cited UNITED STATES PATENTS 2,069,377 2/1937 Matthiessen285-315 X 2,302,856 l`l/1942 Hamon.

2,881,842 4/ 1959 Wilsoy.

2,978,048 4/ 1961 Walker.

3,037,797 6/19'42 Brown.

3,136,367 6/1964 Wright et al.

EDWARD C. ALLEN, Primary Examiner.

RICHARD G. BERKLEY, Assistant Examiner.

